Parapharyngodon alvarengai Freitas 1957

Parapharyngodon cf. alvarengai Freitas, 1957

Hosts (prevalence; range): T. typhonius (6/16; 3–93), and S. cf. similis (1/2; 2).

Site of infection: small and large intestines.

Stage: adult.

Type host and type locality: Trachylepis atlantica (Schmidt) (= Mabuya maculata), Fernando de Noronha Island, Brazil.

Comments: previous studies have discussed the relationships and validity of the genera Thelandros and Parapharyngodon. Some authors validated the second as genus (eg. Freitas 1957; Adamson 1981; Pereira et al. 2011)

and others considered it as subgenus or synonymy to Thelandros (Yamaguti 1961; Chabaud 1965; Gupta et al. 2009). However, the latest studies consider Parapharyngodon as a valid taxon and indicate the principal characters which distinguish it from Thelandros: eggs are released in early stages of cleavage presenting a subterminal operculum; genital cone and papillae surround the cloaca are lack in males; and females present a conical tail ending in a short spike (Pereira et al. 2011; Bursey et al. 2013; Pereira et al. 2017). Characters that distinguish Parapharyngodon species are: the number of papillae in cloaca and tail of males, size of spicules, the structure of the postcloacal lip, and how ovary surrounds the esophagus (Araújo-Filho et al. 2015; Pereira et al. 2017; Santos et al. 2019). Also, Velarde-Aguilar et al. (2015) suggested the importance of Scan Electron Microscopy to analyze cephalic structures (papillae and lips) for the differentiation of species. The 53 valid species of Parapharyngodon are reported in reptiles and amphibians with global distribution being 21 recorded in Neotropical and Caribbean Region (Pereira et al. 2017; Santos et al. 2019). Parapharyngodon alvarengai is characterized by three pairs of caudal papillae (two pairs adanal—one ventral and other lateral; one pair in a proximal region of the caudal appendage), a smooth anterior cloacal lip and a prebulbar ovary (encircling the esophagus) (Freitas 1957; Pereira et al. 2017). We observed the most of these characters; however we were not sure about the morphology of anterior cloacal lip which is necessary to confirm using Scan Electron Microscopy. For South American anurans, there is only one bufonid species recorded as host for P. alvarengai (Luque et al. 2005), but in the present study these two hylids are recorded as new hosts.